These research studies place primary emphasis on cultivation studies of Mycobacterium leprae. Various tissue cultures derived from poikilothermic animals are used as substrates to study growth of the human leprosy bacilli. Major effort has been placed on diploid and haploid cell cultures derived from the Grass Frog, Rana pipiens. These growth studies make use of a specialized procedure with a unique cell-impermeable porous chamber containing the diploid and haploid cell cultures that are maintained for periods up to 90 days at 25 degrees C. on monolayer petri plate cultures of the homologous cell type. The viability of the original M. leprae inoculum is monitored by inoculation of mouse footpads, and the yields of bacilli from the chambers are determined. In addition, limited studies are conducted to evaluate and compare the phagocytic ability of the different cell culture types for M. leprae. Also, the synthetic capabilities of the tissue cultures within the chambers are followed after infection with the acid-fast organism.